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Electrical Discharge Machine - EDM:

Electrical Discharge Machine - EDM Mechanical Engineering Department 1 Die-sinking EDM systems, the electrode (cutting tool) and workpiece are held by the machine tool. The power supply controls the electrical discharges and movement of the electrode in relation to the workpiece. During operation the workpiece is submerged in a bath of dielectric fluid (electrically nonconducting). (Die-Sinking EDM is also called Sinker, Ram-Type, Conventional, Plunge or Vertical EDM)

EDM – Die-Sinking (Plunge):

EDM – Die-Sinking (Plunge) Mechanical Engineering Department 2 The spark discharges are pulsed on and off at a high frequency cycle and can repeat 250,000 times per second. Each discharge melts or vaporizes a small area of the workpiece surface. During normal operation the electrode never touches the workpiece, but is separated by a small spark gap. The amount of material removed from the workpiece with each pulse is directly proportional to the energy it contains. The electrode (plunger) can be a complex shape, and can be moved in X, Y, and Z axes, as well as rotated, enabling more complex shapes with accuracy better than one mil. Plunge EDM is best used in tool and die manufacturing, or creating extremely accurate molds for injection-molding plastic parts.

EDM:

EDM Mechanical Engineering Department 3 A relatively soft graphite or metallic electrode can easily machine hardened tool steels or tungsten carbide. One of the many attractive benefits of using the EDM process. The dielectric fluid performs the following functions: It acts as an insulator until sufficiently high potential is reached . Acts as a coolant medium and reduces the extremely high temp. in the arc gap. More importantly, the dielectric fluid is pumped through the arc gap to flush away the eroded particles between the workpiece and the electrode which is critical to high metal removal rates and good machining conditions.

EDM:

EDM Mechanical Engineering Department 4 The EDM process can be used on any material that is an electrical conductor The EDM process does not involve mechanical energy, therefore, materials with high hardness and strength can easily be machined. Applications include producing die cavity for large components, deep small holes, complicated internal cavities Dimensional accuracy of ± 0.0005 in is achievable. Minimum wall thickness: .01 inch, over 5 inch span Feature to feature positioning: .001

Wire EDM:

Wire EDM Mechanical Engineering Department 5 Wire EDM machines utilize a very thin wire (.0008 to .012 in.) as an electrode. The wire is stretched between diamond guides and carbide that conduct current to the wire and cuts the part like a band saw. Material is removed by the erosion caused by a spark that moves horizontally with the wire.

Slide 6:

Mechanical Engineering Department 6 Intricately detailed automobile part EDM Examples 7075-T6 aluminum back plate latch, EDM cost is less than half the milling cost. These simple, flat shapes, used in food processing, which usually would be stamped, were wire EDMed instead because they required a superior quality edge.